Over the past two decades, the education policy discussion worldwide has shifted, from increasing educational attainment to improving “educational quality”—that is, toward increasing student learning at each level of schooling (Hanushek and Woessman 2008; UNESCO2005). An accelerated pace of international and national testing around the world has contributed to this shift. Despite widespread acceptance of the notion that improving student performance may have a high economic and social payoff, policy analysts in all countries have surprisingly little hard data on which to base educational strategies for raising achievement (UNESCO2005).

A major problem in drawing policy conclusions from analyses within one country or one state or region is that many key macro-educational policy variables, such as teacher recruitment, teacher training, and school supervision, are fairly uniform within such political units. One way to overcome the limits of single-country educational policy research is t ...